Walk down a dairy aisle and you may start to notice how little we've done with the whole concept. Worldwide, there are about 6,000 mammal species, each with its own unique milk, but Americans get at least 97 percent of all our dairy products from one animal. (That would be the cow.) Even at my local Whole Foods, purveyors of exotica like shad roe and that kombucha stuff, there was only a single brand of goat's milk. "EASY TO DIGEST!" reads the desperate carton.

Over at the cheese counter, the situation was a little better. Sheep's milk made a decent showing. But was that it?

"There's a buffalo-milk mozzarella over in the refrigerator section, but yeah," the cheesemonger told me. "I know a chef who's trying to make a pig's-milk cheese. I'm not sure how that's going."

Abroad, things are a little more diverse: Various foreigners drink the milk of the camel, the yak, the water buffalo, the reindeer, the elk and a few other animals. With the exception of the horse, whose milk is fermented and drunk in central Asia as the lightly alcoholic kumis, all dairy animals of any importance are ruminants, a class of mammal whose four-chambered stomachs allow the production of terrific amounts of milk from high-fiber, low-nutrient pasturage. Their large, graspable teats make milking easy. (Inspect the belly of your cat or dog and you'll get an idea why we don't milk our pets: lots of itty-bitty nipples.)

The three dairy animals familiar to Westerners were domesticated between 10,000 B.C. and 8000 B.C. in the Fertile Crescent. Goats and sheep were probably first, followed by cows. All three have since been bred to improve temperament and output, but cows have responded the most profoundly.

The ancestor of the European milch cow was the ox-like wild aurochs, which finally went extinct in the 17th century. The aurochs could be fierce and stubborn, but a few centuries of breeding transformed it into an animal so docile it will actually line up to be milked and so prolific that a single cow produces around 100 pounds of milk a day. The cow's genome, for whatever reason, responded readily to human dabbling. In this, cows are like wolves, from which we've created dog breeds as different as Chihuahuas and Great Danes, and unlike cats, which all look and act pretty much the same despite having been domesticated back in the Neolithic era. Given its genetic pliability, it was probably inevitable that the cow would become a major dairy animal wherever it could survive.

In America, cows never had any real competition. The ice age had scoured the continent of all of its large ruminants, with the exception of the bison, and Native Americans had no dairy tradition for the colonists to adopt. So, as Deborah Valenze recounts in "Milk," Europeans brought cows along with them when they set off for North America and then let these autonomous food factories graze on the continent's unlimited vegetation until their milk or meat was needed. The cows thrived, to say the least: Between 1627 and 1629, while the colonists were fretting about other things, the number of cattle in Virginia grew from 2,000 to 5,000.

The iron fist of cow-milk hegemony isn't just thanks to cows' high output and doziness. Cow's milk has some real aesthetic and practical advantages: It separates itself into cream and milk, so it can be made into an easily drinkable beverage as well as all the luscious cream-based comestibles, such as ice cream and crème fraiche. Its fat content is similar to that of human milk, which makes it familiar to our palates, and its relative blandness makes it an attractive blank slate for the creation of cheeses with a range of flavor profiles and consistencies, from runny Camemberts to rock-hard Goudas.

But what are we missing out on by abstaining from other mammals' milk? Take the goat: Its milk is tangier, richer, and, to reasonable persons, much tastier than cow's milk. The superior flavor owes a great deal to the fact that goat's milk does not separate; the cream is knitted into the milk. Goats produce the most milk of any mammal relative to body size, which would make them attractive to industrial dairies if they weren't so small. At best, dairy goats are the size of a Newfoundland; milk output averages only around a few gallons a day. A direr failing: Goat's milk cannot easily be made into butter.

As for sheep's milk, almost no one in the United States or anywhere else drinks it straight. It has twice the fat of cow's milk and human milk, making it too rich to be very appealing as a beverage. This fattiness endears it to the world's artsier cheesemakers, who find in sheep's milk a profound communicator of terroir.

"The sheep people are a weird bunch," says one chef, who wanted to remain anonymous so as not to offend his favorite cheesemaker. "Sheep are difficult to raise, and fickle. You don't get much yield, and the cheese isn't that popular, so you're talking about an eccentric person. It's very difficult."

Unpalatable fat and protein levels keep some milks off the shelves, but the difficulty of milking recalcitrant beasts can be no less an obstacle. Consider water buffalo, which are raised in Campania, Italy, to make the otherworldly mozzarella di bufala but are otherwise little known in the West. Water buffalo are smart and watchful and have giant horns — in other words, they're dangerous — yet their milk has been a cornerstone of the most dairy-crazed cuisine in the world, that of India, for 1,000 years. Indian cooks use buffalo milk in cream sauces, boil and coagulate it for paneer, or reduce it to a paste called khoa that becomes the basis for desserts such as the rosewater-sweetened gulab jamun. The low availability of water-buffalo milk in the United States limits how authentic an Indian meal you can hope to have, and a few dairies are trying to fill the niche, but water buffalo are difficult animals for noobs to deal with.

One Wisconsin dairyman (a former lieutenant colonel in the Israeli military) who had acquired a herd of dairy buffalo told a newspaper that milking them was more difficult than leading troops into war.

Camel's milk, which is sometimes the only source of water in the arid climates of the Middle East and parts of Africa, isn't much easier to obtain. Gil Riegler, who runs the Oasis Camel Dairy in Ramona, Calif., says a typical camel produces around two gallons of milk a day in two 90-second long bursts and only while a calf is in the act of nursing (from a different teat). And once you've got the milk, you can't do much with it other than drink it. The low-solid content of camel's milk means it cannot be processed into butter or cheese without high-tech intervention.

Nonetheless, Riegler (who has yet to secure to necessary Agriculture Department permits to sell his milk) is a great believer in the product: "Where camel milk is available," he asserts, "people will prefer to drink it." He says camel's milk contains insulin and can improve quality of life for diabetics (seems legit) and cites stories about it treating autism (does not). To aid in water retention, camels consume about eight times as much sodium as cows, so their milk can be weirdly salty, but it can also be sweet. On Bizarre Foods America, Andrew Zimmern sipped some of Riegler's milk and pronounced it "fantastic." But the fact that camel's milk was on a show called Bizarre Foods makes a prima facie case that the American palate may not be quite ready for it.

And pig's milk, alas, is also not quite ready for the American palate. With a little effort, I tracked down the chef I heard about at Whole Foods, the one who's trying to make pig's cheese. It's Edward Lee of Louisville's 610 Magnolia and Top Chef. "Anyone who farms pigs would say that pigs' milk would make an incredible cheese," he says. "The problem is that it's nearly impossible to milk pigs. When sows are lactating, they get very aggressive. They're not docile like cows. They're smart, skittish, suspicious and paranoid. They do not like you to get up in their business."

Lee managed to accumulate a few jars' worth of pigs' milk, from which he made half a cup of pig ricotta that he says was delicious. Getting even such a small amount of milk required jackal-like derring-do: Lee crept up on the sows while they were sleeping, frantically pinched at their tiny nipples, then ran away when they woke up and started to freak out.

If only there were an industry that made pig-milking machines.

"What we've discovered," says Lee, "uh, what we've concluded, you know, is basically that the machine that would fit a pig's teat is a human breast pump. It fits perfectly."

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Phelan is a writer living in Louisville, Ky.